Should I buy my stepdaughter clothes?

My step daughter will bel 23 years old in august. she has lived with my husband and I since she was 11 years old. she use to commute to work about 50 miles. she seemed to love her job in the beginning. my husband co signed for her to get a car so she could have solid transportation. she paid her insurance. she worked for about 8 months and then she got where she lost interest in her job and was late going in. she lost her job. she did not look for another job until I finally I told her my friend has her own business cleaning houses and she could use her help. she did start working with her. she doesn’t work full time and doesn’t bother about looking for a full time job. she barley makes her car payment. we pay her car insurance. we have pleaded with her to get a full time job that has health benefits. she gets very defensive. our family is going on a cruise at the end of june and at first I wasn’t going to pay for my step daughter to go. I felt she should pay her own way if she wanted to go.. she said why should I have to pay. we ended up paying for her. now my dilema is that she wants clothes for the cruise. we have known about the crusie for a very long time. I told my step daughter that she has known about this for a long time and she should pay for her own clothes or should have been saving for this. I feel I shouldn’t buy her the clothes although I feel guilty not doing it. I feel maybe it will be a lesson for her that may encourage her to look for full time work. the other thing is I have a daughter that is 17 years old. she will be 18 in august. she is going to college and works part time. I have purchased clothes for her for college. I always purchase clothes for sarah when she was younger. I feel there is five years difference in their ages and should not have to always give them the same things equally. although at christmas I make sure they have the same amount. this I felt I should stop to because of the age difference. what should I do? should I buy the clothes or not?